For his lecture course at Dartmouth last summer, “Astronomy 3: Exploring the Universe,” Prof. Yorke Brown gave a quiz at week’s end. “Any questions?” he asked, just before one on the life cycle of stars. Just one. Johanna Evans, an English major, wanted to know: “How do you keep from despairing at the immensity of space and the smallness of us?” Professor Brown acknowledged that it was “a beautiful and important question,” but, he wondered, could it wait until after the quiz? Here are excerpts from the follow-up e-mail exchange. Subject line: Despair.

MS. EVANS: I guess the hugeness of what we are studying finally caught up with me once we broke out of the basic principles of physics. It was like opening up an unused compartment in my brain, as though one part were used to think about things that concerned my earthly sphere, and this other newly discovered part was meant to — but not ready to — grapple with HUGE realities. I felt as though the impact of my existence is small, compared to something like the impact of a supernova.

DR. BROWN: Johanna, you are most certainly an infinitesimal in the cold vastness of the cosmos, and yes, you are only one of billions of humans and other creatures who have come before and will come after, and your life is barely a mathematical instant in the span of time. But you are also, just as certainly, a miracle: you are a creature capable of thought, of wonder, of awe. You are a creature capable of recognizing that you are not the center of the Universe. And it is because of that very capacity that you can see in other people the same intrinsic value that you see in yourself. You are capable of love, and so need not despair of insignificance. See you Monday.